Happened to me as well. I found the issue.
Technical part:
It has something to do with the generated query. Sometimes the returned ID is “NULL” instead of the ID itself, I don’t know why it returns NULL, haven’t checked that out yet, but anyways, it results in a faulty query, e.g.: SELECT * FROM WP_POSTS WHERE ID IN (500,100,,400). Notice the double commas. That’s incorrect SQL and crashes the export script.
(Quick) Fix:
Add the following code to the ‘export-media-with-selected-content/export-media-with-content.php‘ file at line number 175:
$ids = array_filter( $ids );
This makes sure all empty values are filtered out of the $ids array.
Hi @newcastlecreativeco and @donnyoexman
Sorry for the late reply and Donny: thanks for you fix.
I’ve just updated the plugin and tested for WP5.8, will publish it soon.